add vdma

src/crab/dma.cr

@@ -91,7 +91,6 @@ class DMA
     end
   end
 
-  # todo: vdma
   def trigger_hdma : Nil
     4.times do |channel|
       dmacnt_h = @dmacnt_h[channel]
@@ -99,6 +98,13 @@ class DMA
     end
   end
 
+  def trigger_vdma : Nil
+    4.times do |channel|
+      dmacnt_h = @dmacnt_h[channel]
+      trigger channel if dmacnt_h.enable && dmacnt_h.start_timing == StartTiming::VBlank.value
+    end
+  end
+
   # todo: maybe abstract these various triggers
   def trigger_fifo(fifo_channel : Int) : Nil
     dmacnt_h = @dmacnt_h[fifo_channel + 1]

src/crab/ppu.cr

@@ -64,6 +64,7 @@ class PPU
       @dispstat.vblank = false
     elsif @vcount == 160
       @dispstat.vblank = true
+      @gba.dma.trigger_vdma
       @gba.interrupts.reg_if.vblank = true if @dispstat.vblank_irq_enable
       @bgref.each_with_index { |bgrefs, bg_num| bgrefs.each_with_index { |bgref, ref_num| @bgref_int[bg_num][ref_num] = bgref.num } }
       draw